Attunement to the fertility status of same-sex rivals: women's testosterone responses to olfactory ovulation cues

Evolutionary theories of mating suggest that changes in fertility across the menstrual cycle play an important role in sexual selection. In line with this framework, the current research examined whether olfactory cues to the fertility of a same-sex rival would prompt hormonal signs of intrasexual competition in women. Women exposed to the scent of another woman close to ovulation subsequently displayed higher levels of testosterone than women exposed to the scent of a woman far from ovulation. Whereas women exposed to the scent of a woman in the mid-luteal phase displayed sizable decreases in testosterone over time, no such decline was observed among women exposed to the scent of a woman near ovulation. Thus, olfactory cues signaling a rival's heightened level of fertility were associated with endocrinological responses in women that could be linked to intrasexual competition.